8. Descriptor Management Services, Continued

8.4 Get Next Selector Increment Value

Some functions such as Allocate Descriptors and Allocate DOS Memory can return more than one descriptor. You must call this function to determine the value that must be added to a selector to access the next descriptor in the array.

To Call

     AX = 0003h

Returns

     Carry flag clear (this function always succeeds)
     AX = Value to add to get to next selector

Programmer's Notes

• Since this function involves descriptor management, it will be rarely needed in 32-bit programs.
• Do not make any assumptions about the value this function will return.
• The increment value returned will be a power of two.

Code Sample:

The following function compiles with Watcom C/C++ version 11.0 or later, and Microsoft Visual C/C++ version 4.0 or later:

// Get difference between consecutive descriptors

int dpmiGetSelectorIncrementValue(void)
	{
	unsigned short increment;	// increment value

	__asm {
		mov	eax, 0x003	// call dpmi host to do mapping
		int	0x31

		mov	increment, ax	// save error code from DPMI, if any
		}

	// return the increment
	return increment;
	}